Method for improving the filling ability of tobacco

ABSTRACT

The present invention relates to a method for improving the fillability of tobacco, as cut tobacco leaves or ribs and/or plant-based tobacco additives with cellular structure, by treating the tobacco material which has 8 to 16 wt. % initial moisture with a treatment gas consisting of nitrogen and/or argon at pressures of 50 to 1,000 bar in either one autoclave or with cascade-type switching in several autoclaves, followed by thermal after-treatment of the tobacco material discharged after decompression has occurred, which is characterised in that the decompression is carried out with at least one holding stage whose pressure corresponds to 3 to 60%, preferably 3 to 30% of the original maximum pressure and that the heating of the system whilst it is under residual pressure is carried out in such a way that the tobacco discharge temperature after pressure reduction is completed lies within the range 10 to 80° C. The temperature increase of the system whilst it is under residual pressure is effected by a holding time, circulation via a heat exchanger and/or by transfer of heated gas, with the reduction in pressure being carried out from the maximum pressure in each case to the pressure of the holding stage within an interval of 20 seconds to 5 minutes and the reduction of the residual pressure being carried out within an interval of 3 seconds to 3 minutes.

[0001] The invention relates to a method for increasing the fillability of tobacco materials, such as for example cut tobacco leaves, ribs or plant-based tobacco additives with cellular structure, by treatment of the tobacco material, which has 8 to 16 wt. % initial moisture, with a treatment gas consisting of nitrogen and/or argon at pressures of 50 to 1,000 bar in either one autoclave or with cascade-type switching in several autoclaves followed by thermal after-treatment of the tobacco material discharged after decompression has occurred.

[0002] The expansion of tobacco with inert gases under high pressures, which is also known as the INCOM expanding method, has shown its advantages over the pressure treatment of tobacco with carbon dioxide, ammonia or volatile organic gases and is known, for example, from U.S. Pat. No. 4,289,148, according to which tobacco material with moisture of more than 20 wt. % is treated in the autoclave at operating temperatures between 0 and 50° C. The pressure reduction takes place within 0.5 to 10 minutes, and in the examples referred to, 1.3 minutes, after which the tobacco discharged is subjected to thermal after-treatment e.g. with saturated steam, during which it is expanded.

[0003] According to DE 31 19 330 A1 a tobacco material with reduced moisture of 10 to 15 wt. % is additionally used at an operating temperature below 50° C., to achieve greater cooling of the tobacco material to be discharged when the tension is released. The pressure reduction times in this case are 1.3 to 2 minutes.

[0004] DE 34 14 625 C2 discloses a cascade method, according to which after cooling of the treatment gas before admitting it into the reactor, cooling of the autoclave or use of an undercooled and liquefied treatment gas, a lower impregnation temperature of the tobacco is [achieved]. The pressure reduction times amount to 0.5 to 10, especially 1 to 2 minutes. The minimum temperatures of the tobacco discharged should be below 0° C.

[0005] Analogously, also according to DE 39 35 774 C2 with a cascade-type expansion method, the necessary low impregnation temperatures of 25/45° C. were achieved by circulating the treatment gas via a cooler.

[0006] Although with this known expanding method good values are obtained as regards the increase in the fillability of tobacco and/or of the degree of expansion, these are relatively expensive due to the necessary cooling of the autoclave or autoclaves and because of the additional cooling of the treatment gas.

[0007] The aim of the invention is to improve the existing INCOM methods and to achieve equally good or better degrees of expansion independently of expensive cooling measures.

[0008] According to the invention a method is therefore proposed of the type initially mentioned in accordance with the patent claim preamble, characterised in that the decompression is carried out with at least one holding stage, whose pressure corresponds to 3 to 60%, preferably 3 to 30% of the original maximum pressure and in that the heating of the system whilst under residual pressure is carried out in such a way that the tobacco discharge temperature following full pressure reduction lies within the range 10 to 80° C.

[0009] Surprisingly it has transpired that with lower tobacco moistures in the range 8 to 16 wt. % the existing theory, of providing a low treatment temperature and/or a low discharge temperature, does not lead to optimal expansion results. On the contrary, only by heating the system whilst it is under residual pressure was it possible to achieve surprisingly good values with regard to the expansion effect and/or the fillability, with the heat of compression being used to advantage and not eliminated, according to the method, and additional cooling of the autoclave or autoclaves being unnecessary.

[0010] The pressure reduction from the maximum pressure in question to the pressure of the holding stage is preferably carried out within an interval of 20 seconds to 5 minutes, whilst the reduction of the residual pressure is carried out within an interval of 3 seconds to 3 minutes.

[0011] Furthermore, to achieve the tobacco discharge temperature according to the invention, it is appropriate to effect the temperature increase by means of a holding time, by circulation of the gas under residual pressure via a heat-exchanger and/or by transferring heated gas from a further autoclave.

[0012] In a further preferred variant of the method, the high pressure treatment or the sequence of high pressure treatment and thermal treatment is carried out several times with the same tobacco material.

[0013] Especially good results are achieved, if the initial moisture of the tobacco material is within the range 10 to 14 wt. % and, furthermore, if the thermal after-treatment of the tobacco material is carried out with saturated steam.

[0014] The method according to the invention is explained below with reference to examples.

EXAMPLE 1

[0015] To carry out the method according to the invention, and also for the comparative tests, the high pressure treatment was carried out with a treatment gas consisting of nitrogen in a laboratory autoclave with a used content of 2 l, wherein to adjust the desired operating temperatures, a casing was used for circulation of the liquid media. The pressure build-up/gas supply to the autoclave took place from below, the pressure reduction/gas discharge from the autoclave took place upwards. To adjust the final pressure a compressor was used, whilst the tobacco temperature was measured in the upper section or upper half of the tobacco filling unit with a thermocouple element.

[0016] The laboratory device for thermal after-treatment of the tobacco consisted of a permeable conveyor belt/wire gauze, which was driven at a speed of approx. 5 cm/s. The tobacco mat guided between baffles was after-treated under a steam nozzle approx. 160 mm wide with a slit-type outlet of approx. 8 mm with approx. 10 kg/h saturated steam.-A steam suction device was situated below the conveyor belt opposite the steam nozzle.

[0017] The tobacco samples treated in this way were spread out in flat trays and conditioned at 21° C. and 60% relative humidity.

[0018] The fillabilities were determined by means of a Borgwaldt density meter and the specific volume converted into ml/g with a nominal moisture of 12 wt. % and a nominal temperature of 22° C. From the data of the untreated comparison sample and the expanded sample, the relative improvement in fillability and/or the degree of expansion is calculated as follows:

Δ%=(F _(E) −F _(B))*100% /F _(B)

[0019] (F_(B)=fillability untreated, F_(E)=fillability expanded)

[0020] A PVC pipe with a perforated bottom inserted was used to receive the tobacco in the autoclave. The gas supply during the pressure build-up took place up to a final pressure of 700 bar. 300 g Virginia blend with 12% moisture was used as tobacco. The test results are shown in the following tables, where T_(A) means the discharge temperature of the tobacco subjected to high-pressure treatment. In test 1, during the pressure reduction, two holding stages each lasting 2 minutes at 400 bar and 100 bar were applied, and in tests 2 and 3 only one holding stage lasting 2 min/4 min at 50 bar was applied. In comparison test no. 4 the pressure reduction took place directly, i.e. without a holding stage in a pressure reduction time of <1 min. TABLE 1 Test results Operating temperature ° C. 60 80 No. Operation pressure reduction T_(A) ° C. Δ % T_(A) ° C. Δ % 1 Holding stage at 400 and 100 16 83 — — bar, each 2 min 2 Holding stage at 50 bar, 2 min 15 93 20 90 3 Holding stage at 50 bar, 4 min 33 93 41 90 4 None (comparison) −25   80  −3   81

[0021] The above tests nos. 1 to 3 with various pressure and time values for the holding stage and two operating temperatures of the autoclave show, in comparison with test 4 with direct pressure reduction, that the holding times with a pre-selected holding stage (pressure) produced a clear increase in the discharge temperature from −25° C. or −3° C. up to +33° C. or +41° C. and, in contrast to the existing technical theory, an increased improvement in fillability in spite of high discharge temperatures.

EXAMPLE 2

[0022] Analogously to example 1, the high-pressure treatment was carried out with 150 g tobacco at an operating temperature of the autoclave of 40° C. During the pressure reduction in test no. 5 a holding stage of 2 min was applied at 50 bar and during the holding time the gas is circulated by means of a circulation pump via a heat exchanger with a temperature of 80° C. This time the gas supply during the pressure reduction and during the circulation took place from above, the gas discharge with holding stage and pressure reduction downwards. A sealing ring between the upper limit of the tobacco insertion container and the autoclave lid guaranteed the direct entry of the gas into the tobacco insertion container. TABLE 2 Test results Operating temperature 40° C. No. Operation during pressure reduction T_(A) ° C. Δ % 5 Holding stage 2 min at 50 bar, circulation    10 79 via heat exchanger (80° C.) 6 None (Comparison) −105 69

EXAMPLE 3

[0023] A procedure similar to that of Example 2 was followed, wherein during pressure reduction, the pressure was kept constant at 50 bar for a holding stage of 1 min and heated gas from a second autoclave, designated the “donor” was introduced into the treatment container. The donor, before the transfer, had a pressure of 100 bar and an operating temperature of 80° C. with a content of 4 l. The gas supply during pressure reduction and during transfer now took place from below, the gas outlet with holding stage and pressure reduction upwards. TABLE 3 Test results Operating temperature 40° C. No. Operation during pressure reduction T_(A) ° C. Δ % 7 Holding stage 1 min at 50 bar, transfer 16 89 from donor, pressure 100 bar Operating temperature 60° C.

[0024] In contrast to example 1, in which the heating, by means of a holding time with a pre-selected holding stage/pre-selected pressure presupposes a raised operation temperature, examples 2 and 3 above show that the circulation according to example 2 via a heat exchanger or the transfer of gas from the donor according to example 3 with a constant holding stage/constant pressure also lead to a raised operating temperature when the operating temperature of the gas-containing treatment container, designated the “acceptor” is 40° C. The variant involving a transfer from the donor container according to example 3 in particular leads to a clear increase in the fillability improvement over the comparative test no. 6 in example 2.

[0025] For interpretation of these surprising results it can be assumed that the heating of the high-pressure-treated tobacco under residual pressure leads to a preliminary expansion in the autoclave, producing additional improvements in fillability, which cannot be achieved with the known method. To confirm this assumption in the following example 4, the pressure treatment was carried out without thermal after-treatment with saturated steam, to test a possible effect of a preliminary expansion, with direct conditioning of the samples treated. It is true that the improvements in fillability without thermal after-treatment are small, but in the following example 4, an additional effect appears during heating under residual pressure.

EXAMPLE 4

[0026] 150 g tobacco were subjected to high-pressure treatment at an operating temperature of the autoclave of 60° C., and the tobacco was not subjected to thermal after-treatment after complete pressure reduction. During pressure reduction there was a holding stage of 1 min at 50 bar with a transfer of heated gas from a second autoclave analogous to example 3, the donor having a pressure of 200 bar and an operating temperature of 80° C. before the transfer. In the comparative test no. 9 the pressure reduction took place directly and without a holding stage. TABLE 4 Test results Operating temperature 60° C. No. Operation during pressure reduction T_(A) ° C. Δ % 8 Holding stage 1 min at 50 bar, transfer   19 21 from donor, pressure 200 bar Operating temperature 80° C. 9 None (Comparison) −69  8

[0027] The above results confirm the assumption of an albeit slight preliminary expansion before the thermal after-treatment with saturated steam during heating of the high-pressure-treated tobacco whilst it is under residual pressure.

[0028] The following examples 5 and 6 show a further embodiment of the method according to the invention, in which the high-pressure treatment/high-pressure treatment and thermal after-treatment are carried out several times with the same tobacco material.

EXAMPLE 5

[0029] In a first stage, 150 g tobacco were subjected to high-pressure treatment at an operating temperature of the autoclave of 60° C., analogously to example 3 by transfer of heated treatment gas from the donor with a holding stage with constant pressure. Before the transfer the donor had a pressure of 300 bar and an operating temperature of 80° C.; the holding stage was adjusted to 1 min at 200 bar.

[0030] The tobacco material from the first stage, expanded and conditioned according to test no. 10, was used as base material for a further cycle of treatment consisting of high-pressure treatment and thermal after-treatment. The high-pressure treatment was carried out with 100 g tobacco and at an operating temperature of the autoclave of 60° C., and a holding stage of 1 min at 100 bar was provided during pressure reduction. The donor container before the transfer, possessed a pressure of 200 bar at an operating temperature of 80° C., the results of this test and test no. 10 are shown by Table 5. TABLE 5 Test results Operating temperature 60° C. No. Operation during pressure reduction T_(A) ° C. Δ % 10 Holding stage 1 min at 200 bar, 26  86 transfer from donor, pressure 300 bar Operating temperature 80° C. 11 Holding stage 1 min at 100 bar, 24 116 transfer from donor, pressure 200 bar (Treatment Operating temperature 80° C. of expanded tobacco from test 10)

EXAMPLE 6

[0031] A procedure analogous to that of example 5 was followed, wherein however in this case two identical pressure treatment cycles were carried out one after the other, followed by thermal after-treatment. The results are as follows. Operating temperature 60° C. No. Operation during pressure reduction T_(A) ° C. Δ % 12 Holding stage 1 min at 100 bar, 30 103 transfer from donor, pressure 200 bar (double Operating temperature 80° C. pressure treatment followed by thermal treatment)

[0032] Whereas the expanded tobacco material of stage 1 from example 5 was used for renewed treatment in stage 2, in this example 6 the pressure treatment cycle was carried out twice in succession and only then was the pressure-treated tobacco material subjected to the thermal after-treatment. Both methods are based on the principle of a multiple expansion by repetition of the sequence of high-pressure treatment and thermal after-treatment or one repeated high-pressure treatment only followed by thermal after-treatment.

[0033] Example 5 shows that the effect of the first expansion stage can be further increased by the renewed treatment in stage 2 and a tobacco material with extremely high fillability is obtained. Example 6 is simpler, due to the omission of an after-treatment stage, but does not reach the maximum value of example 5. 

1. Method for improving the fillability of tobacco, as cut tobacco leaves or ribs and/or plant-based tobacco additives with cellular structure, by treatment of the tobacco material which has 8-16 wt. % initial moisture with a treatment gas consisting of nitrogen and/or argon at pressures of 50 to 1,000 bar, in either one autoclave or with cascade-type switching, in several autoclaves, followed by thermal after-treatment of the tobacco material discharged after decompression has occurred, characterised in that the decompression is carried out with at least one holding stage, whose pressure corresponds to 3 to 60%, preferably 3 to 30% of the original maximum pressure and that the heating of the system whilst it is under residual pressure is carried out in such a way that the tobacco discharge temperature lies within the range 10 to 80° C. after pressure reduction is completed.
 2. Method according to claim 1, characterised in that the initial moisture of the tobacco material lies within the range 10 to 14 wt. %.
 3. Method according to claims 1 to 2, characterised in that the temperature increase of the system whilst it is under residual pressure is effected by a holding time.
 4. Method according to claims 1 to 3, characterised in that the temperature increase is effected by circulation of the gas under residual pressure via a heat exchanger.
 5. Method according to claims 1 to 4, characterised in that the temperature increase of the system whilst it is under residual pressure is effected by transfer of heated gas.
 6. Method according to claims 1 to 5, characterised in that the pressure reduction from the maximum pressure in each case to the pressure of the holding stage is carried out within an interval of 20 seconds to 5 minutes.
 7. Method according to claims 1 to 6, characterised in that the reduction of the residual pressure is carried out within an interval of 3 seconds to 3 minutes.
 8. Method according to claims 1 to 7, characterised in that the high-pressure treatment or the sequence of high-pressure treatment and thermal treatment is carried out several times with the same tobacco material.
 9. Method according to claims 1 to 8, characterised in that the thermal after-treatment of the tobacco material is carried out with saturated steam. 